930 starting problem
 

I have a 79 930 that would not start twice out of 20-30 starts. When I turn the key, I just hear a faint hum (probably the fuel pump?), but the engine does not turn over. The lights and radio work fine. I kick started the car both times, and the car started fine afterwards both times. It has been suggested that there may be a flat spot or dead spot in the starter, and I should replace the starter. Opinions?

Rusty ground strap, bad solenoid or failing ignition lock?

Pick yours...

Mine had bad ignition lock...i checked it by "hot wiring" it.

Thanks for the response. I guess for me the real issue is how do you trouble shoot the problem when it does not happen very frequently. The shop said to bring it in and they would start it, hoping that sooner or later it would not start and then they could trouble shoot the problem, but I dont want to have to pay them for starting my car for hours, never having it not start, and then having them recommend replacement of the starter/solenoid/ignition switch hoping that was the problem. I guess I could continue to drive it until it breaks, but I really dont want to get stuck somewhere when it decides not to start.

sometimes you have to take a chance and replace the most likely culprit. that would be the starter in your case. they don't always oblige when troubleshooting the problem.

Try replacing the easy things 1st.
1. Ground strap
2. Ignition switch(plugs into back of
your Ignition lock.
3. Starter (replace with the high torque
model)
I bet one of these is your problem.
Good luck!!!!

It is very common for the ignition switch to go bad in old 911s. The symptom is everything working normally in the start sequence until you get to the bottom of the arc - then nothing. The starter doesn't engage because the power isn't getting to it. Real easy to check, test the starter relay for power when a helper hits the key.
See project 91 in Wayne's book.

I have tested starters almost every day for about 24yrs now and the dead spot on the armature is very rare. It does happen but man is it rare. Other people may have other experience's but it seems like less likely.